And Donald Trump has taken to saying that Hillary Clinton is using her gender against him.

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DONALD TRUMP: If she didn't play the woman's card, she would have no chance - I mean zero - of winning.

MONTAGNE: Gender could be a decisive factor in a general election matchup between Trump and Clinton. And some experts say Trump is using the man card. Here is NPR's Asma Khalid.

ASMA KHALID, BYLINE: The gender gap in American politics is nothing new. Jennifer Lawless teaches at American University. And she says men and women often don't see eye to eye.

JENNIFER LAWLESS: In every presidential election since 1980, women have been more likely than men to support the Democratic candidate.

KHALID: But this year, that gender gap seems to be growing into a gender gulf. Polls show about 70 percent of women have an unfavorable opinion of Trump, who made these comments over the weekend in Spokane, Wash.

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TRUMP: Did you hear that Donald Trump raised his voice while speaking to a woman? Oh, I'm sorry. I'm sorry. I mean, all of the men, we're petrified to speak to women anymore. We may raise our voice. You know what? The women get it better than we do, folks.

KHALID: Dan Cassino is a political scientist at Fairleigh Dickinson University. He says all this talk about women is actually directed at guys.

DAN CASSINO: This is an appeal, saying basically to other men, hey, the women are ganging up on us. The women are using their gender to get power from us. All the women are going to get together and vote for Hillary Clinton. We have to band together as men to stop Hillary Clinton.

KHALID: Cassino says Trump is playing on gender resentment.

CASSINO: He is your textbook case of what it looks like when someone is trying to assert masculinity in the most extreme way possible.

KHALID: And gender roles do make a difference for some voters. Cassino told me during a recent presidential poll, he asked voters this question.

CASSINO: There are an increasing number of households in which the woman makes more money than the man. How about your household?

KHALID: He found when men were asked that question at the beginning of the poll, they were more likely to support Trump over Clinton. And that happened regardless of the actual answer to the income question. But gender bias seems to cut both ways. Clinton used the woman's card attack as a hugely successful fundraiser, selling actual cards. Here is Jennifer Lawless again.

LAWLESS: That kind of messaging can be helpful for a Democrat, and particularly a Democratic female candidate, who wants to appeal to donors and activists.

KHALID: And if Clinton has been playing a woman card by focusing on pay equity or childcare, then...

KELLY DITTMAR: Surely Donald Trump has been playing the man card by talking about the ways in which his opponents are in fact not masculine enough for the office.

KHALID: That's Kelly Dittmar with the Rutgers Center for American Women and Politics. And here's what she's talking about.

Don't worry about it, little Marco. He referred to my hands. If they are small, something else must be small. I guarantee you there is no problem.

KHALID: So the question is, does all this messaging have an effect on voter turnout? Deborah Jordan Brooks at Dartmouth College has studied the connection between gender, voter participation and negative ads. This election cycle, she says, is very unpredictable. But her research in the past found women weren't really affected one way or the other by negative campaigns. Men were.

DEBORAH BROOKS: Independent men were especially likely to vote after seeing uncivil negative messages - the kinds of attacks that throw in extra insults.

KHALID: In other words, insults seem to mobilize men.

JORDAN BROOKS: Incivility produced a real gender difference between men and women. Men seemed to like it.

KHALID: So what can we learn from all this? Well, Republicans usually try to shrink the gender gap by courting women. But maybe Trump has calculated it makes more sense to embrace his gender gap and focus on men. Asma Khalid, NPR News. Transcript provided by NPR, Copyright NPR.